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* Copyright 2014 Google Inc.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
#ifndef GrConvexPolyEffect_DEFINED
#define GrConvexPolyEffect_DEFINED
#include "GrDrawTargetCaps.h"
#include "GrFragmentProcessor.h"
#include "GrProcessor.h"
#include "GrTypesPriv.h"
class GrInvariantOutput;
class SkPath;
* An effect that renders a convex polygon. It is intended to be used as a coverage effect.
* Bounding geometry is rendered and the effect computes coverage based on the fragment's
* position relative to the polygon.
class GrConvexPolyEffect : public GrFragmentProcessor {
enum {
kMaxEdges = 8,
* edges is a set of n edge equations where n is limited to kMaxEdges. It contains 3*n values.
* The edges should form a convex polygon. The positive half-plane is considered to be the
* inside. The equations should be normalized such that the first two coefficients are a unit
* 2d vector.
* Currently the edges are specified in device space. In the future we may prefer to specify
* them in src space. There are a number of ways this could be accomplished but we'd probably
* have to modify the effect/shaderbuilder interface to make it possible (e.g. give access
* to the view matrix or untransformed positions in the fragment shader).
static GrFragmentProcessor* Create(GrPrimitiveEdgeType edgeType, int n,
const SkScalar edges[]) {
if (n <= 0 || n > kMaxEdges || kHairlineAA_GrProcessorEdgeType == edgeType) {
return NULL;
return SkNEW_ARGS(GrConvexPolyEffect, (edgeType, n, edges));
* Creates an effect that clips against the path. If the path is not a convex polygon, is
* inverse filled, or has too many edges, this will return NULL. If offset is non-NULL, then
* the path is translated by the vector.
static GrFragmentProcessor* Create(GrPrimitiveEdgeType, const SkPath&,
const SkVector* offset = NULL);
* Creates an effect that fills inside the rect with AA edges..
static GrFragmentProcessor* Create(GrPrimitiveEdgeType, const SkRect&);
virtual ~GrConvexPolyEffect();
const char* name() const override { return "ConvexPoly"; }
GrPrimitiveEdgeType getEdgeType() const { return fEdgeType; }
int getEdgeCount() const { return fEdgeCount; }
const SkScalar* getEdges() const { return fEdges; }
void getGLProcessorKey(const GrGLSLCaps&, GrProcessorKeyBuilder*) const override;
GrGLFragmentProcessor* createGLInstance() const override;
GrConvexPolyEffect(GrPrimitiveEdgeType edgeType, int n, const SkScalar edges[]);
bool onIsEqual(const GrFragmentProcessor& other) const override;
void onComputeInvariantOutput(GrInvariantOutput* inout) const override;
GrPrimitiveEdgeType fEdgeType;
int fEdgeCount;
SkScalar fEdges[3 * kMaxEdges];
typedef GrFragmentProcessor INHERITED;